Promoter dependence of transgene expression by lentivirus-transduced human blood-derived endothelial progenitor cells

Peripheral blood- derived endothelial progenitor cells (EPCs) have considerable potential for the autologous therapy of vascular lesions or ischemic tissues. By introducing stable genetic modifications into these cells, this potential might be further enhanced. We investigated to what extent transgene expression can be controlled by using different transgene promoters. This was investigated in early- or late-outgrowth human EPCs obtained by culturing blood mononuclear cells for 1 or 4 weeks on type 1 collagen in medium containing endothelial growth supplements. A large fraction of these cells were stably transduced using lentiviral vectors for expression of the enhanced green fluorescent protein (EGFP). Transgene expression in vitro or in vivo after injection into nude mice was highest when under the control of the cytomegalovirus (CMV) promoter, intermediate with the EF1alpha promoter, and lowest with the phosphoglycerate kinase promoter. When blood mononuclear cells were cultured for 1 week in the absence of endothelial growth supplements, CMV promoter- driven expression of EGFP was two orders of magnitude lower than in similarly transduced EPCs. Our results show that lentiviral vectors are useful tools for the stable introduction of exogenous genes into EPCs and for their expression at desired levels using the appropriate gene promoter.